1. Field of Use
The present invention relates to monitoring the operation of computer systems and, more particularly, to apparatus and methods for selectively capturing trigger conditions.
2. Prior Art
A recurring problem in monitoring the performance and operation of computer systems, for example, the states appearing on system buses during operation, is the ability of the user of a monitoring apparatus to selectively capture the conditions to be monitored and detected. For example, the user of a monitoring apparatus of the prior art generally has the ability to capture all of the events occurring from a single source within a given time after initiation of the monitoring process, but not the ability to selectively capture information related to specific, selected events that might occur independently from several sources and at any time after start of the monitoring. That is, the monitoring apparatus of the prior art operates in much the same manner as a tape recorder, turn it on and it records everything that happen until it runs out of tape. Unless, therefore, the storage capabilities of a monitoring device are impracticably large, the user has difficulty in capturing events that may occur only at infrequent intervals or only long after the monitoring process has started and may not, in fact, capture the events of interest because the monitoring device's data recording apparatus becomes saturated, or filled with data. This is particularly true in the case of events which are either intermittent, such as certain types of failures, or which happen only infrequently in the normal operation of a system. In addition, and contributing to the problem, the monitoring devices of the prior art are generally not capable of selectively defining and capturing events of interest, but must capture much data which is not of interest in order to capture the data that is of interest, and cannot monitor events from a variety of sources, making repetitive monitoring operations necessary to establish correlations between events at various sources.